Like a great girlfriend, it's charming, beautiful, amusing and sometimes a little irritating.
The quest is relatively short, but you still feel like you've traveled a lot of ground and actually achieved something. Partially, it's because throughout the levels, there are huge scenes of trolls and elves fighting, so whenever you finish a mission or knock out a key catapult, you feel like you're part of a major struggle. The last level, which I think is an homage to Bowser's Airship from Super Mario Bros. 3, is also superbly paced and intense, and when you finally defeat the final boss it's a great feeling.
Controls are generally pretty good, although the camera gets caught in places. Battles are usually entertaining, especially when you have a wide variety of ways to dish out damage. Puzzles are almost always repeated in sets of three, which is slightly frustrating when you come across a boring/challenging one you know you'll have to do twice more, but again, you do feel like you accomplished something afterwards, not just pushed blocks around.
The most repetitive fight is taking out shadow trolls in the shadow world, which you have to do five times. But the feeling of acquiring a new Elemental Warrior (each of which has an amusing, moving cutscene when you unlock it) is always great, and you never feel like you wasted time.
The score is as good as the Lord of the Rings, and seems to have some nods to Star Wars and LotR in the themes. LotR actually seems to have made a major influence on the game, especially the look for Thorn's Castle (which looks somewhat like Barad-Dur), and the horse sequences (charging through a hundred trolls, anyone?).
There's not that much to do when you've finished except to try for insanely high scores to unlock Achievements, and do some co-op, which hurts its value somewhat.
It makes a fabulous weekend rental though.